Conventionally, in a semiconductor device manufacturing field, there is known a plasma processing apparatus using inductively coupled plasma (ICP) as an apparatus for performing a process such as a film forming process or an etching process on a substrate such as a semiconductor wafer.
As for a processing gas supply structure of a plasma processing apparatus using ICP, in a plasma processing apparatus having a high frequency coil installed above a processing chamber, there is known a structure, for example, in which a processing gas supply mechanism including an annular hollow pipe is provided in a space between a high frequency coil and a substrate, and a processing gas is introduced into a space above the substrate from a multiple number of gas discharge openings formed at the inner side of the hollow pipe (see, e.g., Patent Document 1).
Further, in a plasma processing apparatus having a high frequency coil installed at a sidewall of a processing chamber, there is known a structure, for example, in which a processing gas is discharged from an upper center of the processing chamber to a space above a substrate (see, e.g., Patent Document 2).
All the above-described processing gas supply structures are of a type using a nozzle shape structure having openings such as holes or slits. In case of the plasma processing apparatus having the high frequency coil installed above the processing chamber, if there exists a large structure for introducing a gas to above the substrate, a processing state of the substrate may become non-uniform because the substrate is blocked by the large structure. Further, in case that a gas diffusion space is installed between the substrate and the high frequency coil, a means to prevent an electric discharge in this space is needed. For this reason, an area for discharging the gas is basically limited to a central area and an outer peripheral area of the substrate.    Patent Document 1: Japanese Patent Laid-open Publication No. 2001-85413    Patent Document 2: Japanese Patent No. 3845154
As described above, in the conventional plasma processing apparatus and the processing gas supply structure thereof, since the area for discharging the gas is limited, it is difficult to improve processing uniformity within a wafer surface by controlling a supply state of the processing gas.